Illuminator and projector

ABSTRACT

An illuminator includes: a light source that emits light; a first lens array including a plurality of first lenslets; a second lens array including a plurality of second lenslets corresponding to the plurality of first lenslets; a polarization conversion element that converts light fluxes from the second lens array into polarized light fluxes and outputs the polarized light fluxes; and a superimposing lens that superimposes sub-light fluxes from the polarization conversion element, wherein the plurality of first lenslets and the plurality of second lenslets are each arranged in a matrix, the polarization conversion element is formed of a plurality of columns of polarization conversion units that convert the light fluxes from the plurality of second lenslets into the polarized light fluxes on a column basis, and the number of columns of the polarization conversion units is fewer than the number of columns of the first lenslets and the second lenslets.

BACKGROUND

1. Technical Field

The present invention relates to an illuminator and a projector.

2. Related Art

There has been a known illuminator including a light source that emitslight, a first lens array formed of a plurality of first lenslets, asecond lens array formed of a plurality of second lenslets correspondingto the plurality of first lenslets, a polarization conversion elementthat converts light fluxes from the second lens array into polarizedlight fluxes and outputs them, and a superimposing lens thatsuperimposes sub-light fluxes from the polarization conversion elementon one another (see International Publication No. 97/50012, forexample). The first lens array, the second lens array, and thesuperimposing lens form alight homogenizing system that homogenizes thein-plane optical intensity distribution of the light (what is calledlens integrator system).

In the illuminator of related art, the plurality of first lenslets andthe plurality of second lenslets are each arranged in a matrix (alsocalled row-column matrix). The polarization conversion element is formedof a plurality of columns of polarization conversion units that convertlight fluxes from the plurality of second lenslets into polarized lightfluxes on a column basis. Further, the number of columns of the firstlenslets and the number of columns of the second lenslets are the sameas the number of columns of the polarization conversion units.

The illuminator of related art, which includes the lens integratorsystem and the polarization conversion element, can output polarizedlight having a homogenized in-plane optical intensity distribution andhence can be suitably used with an apparatus using “polarized lighthaving a homogenized in-plane optical intensity distribution” (such asliquid crystal apparatus).

In a technical field of illuminators, an illuminator is always requiredto use light more and more efficiently, which holds true for theilluminator including the lens integrator system and the polarizationconversion element described above.

SUMMARY

An advantage of some aspects of the invention is to provide anilluminator capable of using light more efficiently than an illuminatorof related art. Another advantage of some aspects of the invention is toprovide a projector including the illuminator described above and usinglight efficiently.

It is known that the loss of light that passes through a polarizationconversion element typically decreases as the size of a polarizationconversion unit increases. In view of this fact, it is conceivable toincrease the size of each polarization conversion unit by reducing thenumber of columns of the polarization conversion units. A studyconducted by the present inventor, however, shows that reducing thenumber of columns of the polarization conversion units hardly allows anilluminator of related art to use light more efficiently, as shown inExperimental Example described later.

The present inventor has further conducted a study based on the resultdescribed above and showed that setting the number of columns of thepolarization conversion units to differ from the number of columns ofthe first and second lenslets, that is, setting the number of columns ofthe polarization conversion units to be fewer than the number of columnsof the first and second lenslets, allows an illuminator to use lightmore efficiently than an illuminator of related art as shown inExperimental Example described later. The present inventor has thusattained the invention. The invention is implemented as follows.

[1] An illuminator according to an aspect of the invention includes alight source that emits light, a first lens array including a pluralityof first lenslets, a second lens array including a plurality of secondlenslets corresponding to the plurality of first lenslets, apolarization conversion element that converts light fluxes from thesecond lens array into polarized light fluxes and outputs the polarizedlight fluxes, and a superimposing lens that superimposes sub-lightfluxes from the polarization conversion element. The plurality of firstlenslets and the plurality of second lenslets are each arranged in amatrix. The polarization conversion element is formed of a plurality ofcolumns of polarization conversion units that convert the light fluxesfrom the plurality of second lenslets into the polarized light fluxes ona column basis. The number of columns of the polarization conversionunits is fewer than the number of columns of the first lenslets and thesecond lenslets.

The illuminator according to the aspect of the invention, in which thenumber of columns of the polarization conversion units is fewer than thenumber of columns of the first lenslets and the second lenslets, can uselight more efficiently than an illuminator of related art, as shown inExperimental Example described later.

The illuminator according to the aspect of the invention, which includesthe lens integrator system and the polarization conversion element as inthe case of an illuminator of related art, can output polarized lighthaving a homogenized in-plane optical intensity distribution and hencecan be suitably used with an apparatus using “polarized light having ahomogenized in-plane optical intensity distribution.”

Each of the polarization conversion units includes a polarizationseparation layer that transmits one of the linearly polarized lightcomponents contained in the light fluxes from the second lenslets andreflects the other linearly polarized light component in the directionperpendicular to an illumination optical axis, a reflection layer thatreflects the other linearly polarized light component having beenreflected off the polarization separation layer in the directionparallel to the illumination optical axis, and a wave plate thatconverts the other linearly polarized light component having beenreflected off the reflection layer into the one linearly polarized lightcomponent. The polarization conversion unit may convert the light fluxesfrom the second lenslets in a single column or may convert the lightfluxes from the second lenslets in two or more columns.

The “polarized light” used herein is not necessarily one type ofpolarized light in an exact sense but may be light practically usable asone type of polarized light.

[2] In the illuminator according to the aspect of the invention, theinterval between the arranged polarization conversion units ispreferably greater than the width of each of the first lenslets.

In the aspect of the invention, the interval (distance) between thearranged polarization conversion units may be equal to the width of eachof the first lenslets, but the configuration described above allows theilluminator to use light more efficiently.

[3] In the illuminator according to the aspect of the invention, thenumber of columns of the first lenslets and the second lenslets ispreferably greater than the number of columns of the polarizationconversion units by one, and the number of columns of the first lensletsand the second lenslets is preferably an odd number.

The configuration described above allows the optical path to bereasonably set with the number of columns of the first lenslets and thesecond lenslets not being greatly different from the number of columnsof the polarization conversion units.

[4] In the illuminator described above, the number of columns of thefirst lenslets and the second lenslets is preferably five, and thenumber of columns of the polarization conversion units is preferablyfour.

The configuration described above allows the lens integrator system andthe polarization conversion element to be configured in a relativelysimilar manner in which those typically used at present are configured,whereby the optical path can be reasonably set.

[5] In the illuminator described above, light incident on the firstlenslets in a column positioned along a center line (hereinafterreferred to as central column) among the plurality of first lensletspreferably enters the second lens array along an optical axis extendingalong “a plane that contains a central axis of the first lens array andextends along the columns of the first lens array (hereinafter referredto as reference plane).” Light incident on the first lenslets in columnson both sides of the central column preferably enters the second lensarray along optical axes that approach the reference plane. Lightincident on the first lenslets in outermost columns among the pluralityof first lenslets preferably enters the second lens array along opticalaxes that extend away from the reference plane.

The configuration described above allows the light from the second lensarray to be outputted as polarized light through the polarizationconversion units arranged in a reduced number of columns.

[6] A projector according to another aspect of the invention includesany of the illuminators described above, a light modulator thatmodulates light from the illuminator in accordance with imageinformation, and a projection system that projects light from the lightmodulator.

The projector according to the aspect of the invention, which includesany of the illuminators described above capable of using light moreefficiently than an illuminator of related art, uses light efficiently.

[7] In the projector according to the aspect of the invention, the lightmodulator is preferably a liquid crystal light modulator.

The invention is suitably applicable to a projector including a liquidcrystal light modulator.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a plan view showing an optical system of a projector accordingto an embodiment.

FIGS. 2A and 2B describe an illuminator according to the embodiment.

FIGS. 3A and 3B describe an illuminator according to ExperimentalExample.

FIGS. 4A and 4B describe another illuminator according to ExperimentalExample.

FIG. 5 shows how light is divided in another illuminator according toExperimental Example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An illuminator and a projector according to an embodiment of theinvention will be described below with reference to the drawings.

EMBODIMENT

FIG. 1 is a plan view showing an optical system of a projector 1000according to an embodiment. In FIG. 1, a light source 110 is drawn in across-sectional form. The same holds true for the other plan views.

FIGS. 2A and 2B describe an illuminator 100 according to the embodiment.FIG. 2A shows a first lens array 120 viewed from the side where a secondlens array 130 is present. FIG. 2B is a plan view showing an opticalsystem of the illuminator 100. The broken-line arrows in FIG. 2Brepresent optical axes of sub-light fluxes from the first lens array 120toward the second lens array 130.

It is noted that FIGS. 1, 2A, and 2B are schematic views and the shapeof each optical element in the figures does not necessarily reflect theactual shape in an exact sense.

In the following description, three directions perpendicular to oneanother are called a z-axis direction (direction representingillumination optical axis 100 ax in FIG. 1), an x-axis direction(direction parallel to plane of view in FIG. 1 and perpendicular to zaxis), and a y-axis direction (direction perpendicular to plane of viewin FIG. 1 and perpendicular to z axis).

In the following description, rows and columns are defined as follows:those extending along the x-axis direction are called rows, and thoseextending along the y-axis direction are called columns.

The projector 1000 according to the embodiment includes an illuminator100, a color separation/light guiding system 200, three liquid crystallight modulators 400R, 400G, and 400B that modulate red light, greenlight, and blue light respectively, a cross dichroic prism 500, and aprojection system 600, as shown in FIG. 1.

The illuminator 100 includes a light source 110, a concave lens 90, afirst lens array 120, a second lens array 130, a polarization conversionelement 140, and a superimposing lens 150. The illuminator 100 emitslight containing red light, green light, and blue light as illuminationlight (that is, light usable as white light) along the illuminationoptical axis 100 ax.

The light source 110 includes an arc tube 10 and a reflector 20, asshown in FIGS. 1 and 2B. The light source 110 outputs light from a lightemitting portion 13 (which will be described later) toward an area to beilluminated, and the light from the light emitting portion 13 isconvergent light having a central axis that coincides with theillumination optical axis 100 ax. Reference character c1 denotes thecenter of the light emitting portion 13.

The arc tube 10 includes a lamp body 12 that accommodates the lightemitting portion 13, a pair of sealing portions 14 and 16 extending fromboth sides of the lamp body 12, a pair of electrodes disposed along theillumination optical axis 100 ax, a pair of metal foils sealed in thepair of sealing portions 14 and 16, and a pair of lead wireselectrically connected to the pair of metal foils. A variety of arctubes that emit high-intensity light can be employed as the arc tube 10,such as a metal-halide lamp, a high-pressure mercury lamp, and anultrahigh-pressure mercury lamp. The light emitting portion 13 ispositioned in the vicinity of a first focal point of a reflectionsurface 24, which will be described later. The light emitting portion 13emits light containing red light, green light, and blue light.

The requirements and other factors of the components of the arc tube 10are as follows by way of example: The lamp body 12 and the sealingportions 14 and 16 are made of quartz glass or any other suitablematerial, and the lamp body 12 encapsulates mercury, a rare gas, and atrace of halogen. The electrodes are, for example, tungsten electrodes,and the metal foils are, for example, molybdenum foils. The lead wiresare made, for example, of molybdenum or tungsten.

The reflector 20 is disposed at the first sealing portion 14, which isone of the pair of sealing portions 14 and 16, and reflects the lightemitted from the light emitting portion 13 toward the area to beilluminated. The reflector 20 has an opening 22, which the first sealingportion 14 of the art tube 10 is inserted into and bonded to, and areflection surface 24, which reflects light toward the area to beilluminated. The reflection surface 24 has an ellipsoidal shape andreflects the light emitted from the light emitting portion 13 positionedin the vicinity of the first focal point of the reflection surface 24.The reflected light converges to a point in the vicinity of a secondfocal point of the reflection surface 24 that is located closer to thearea to be illuminated. The reflector 20 is fixed to the first sealingportion 14 with cement or any other suitable inorganic adhesive withwhich the opening 22 is filled.

A suitable base material of which the reflection surface 24 is made can,for example, be crystallized glass or alumina (Al₂O₃). Avisible-light-reflection layer formed of a dielectric multilayer filmmade, for example, of titanium oxide (TiO₂) and silicon oxide (SiO₂) isformed on the reflection surface 24.

The concave lens 90 converts the convergent light from the light source110 into substantially collimated light. The concave lens 90 is disposednext to the reflector 20 on the side where the area to be illuminated ispresent, as shown in FIGS. 1 and 2B. The concave lens 90 transmits thelight from the reflector 20 toward the first lens array 120.

The first lens array 120, the second lens array 130, and thesuperimposing lens 150 form a light homogenizing system that homogenizesthe in-plane optical intensity distribution of the light to be incidenton the light modulators (what is called lens integrator system).

The first lens array 120 includes a plurality of first lenslets 122,which divide the light having passed through the concave lens 90 into aplurality of sub-light fluxes, as shown in FIGS. 1 and 2A. The firstlens array 120 serves as a light flux dividing optical element thatdivides the light from the light source 110 into a plurality ofsub-light fluxes, and the plurality of first lenslets 122 are arrangedin a matrix of seven rows and five columns in a plane perpendicular tothe illumination optical axis 100 ax. Although not described in detail,the exterior shape of each of the first lenslets 122 (a rectangle havinga transverse/longitudinal (x-axis direction/y-axis direction) ratio of4:3) is substantially similar to the exterior shape of an imageformation area of each of the liquid crystal light modulators 400R,400G, and 400B. The exterior shape of each of the first lenslets is notlimited to the shape described above and may be any shape that issubstantially similar to the exterior shape of the image formation areaof each of the light modulators.

The second lens array 130 includes a plurality of second lenslets 132corresponding to the plurality of first lenslets 122 in the first lensarray 120. The second lens array 130 in conjunction with thesuperimposing lens 150 has a function of focusing images of the firstlenslets 122 in the vicinity of the image formation area of each of theliquid crystal light modulators 400R, 400G, and 400B. The second lensarray 130 is so configured that the plurality of second lenslets 132 arearranged in a matrix of seven rows and five columns in a planeperpendicular to the illumination optical axis 100 ax.

As described above, in the illuminator 100, the number of columns of thefirst lenslets 122 and the second lenslets 132 is five. That is, thenumber of columns of the first lenslets 122 and the second lenslets 132is an odd number.

In the illuminator 100, the light incident on the first lenslets in thecolumn positioned along the center line (hereinafter referred to ascentral column) among the plurality of first lenslets 122 enters thesecond lens array 130 along an optical axis extending along “a planethat contains the central axis of the first lens array 120 (whichcoincides with the illumination optical axis 100 ax in the embodiment)and extends along the columns in the first lens array 120 (hereinafterreferred to as reference plane, which coincides with the illuminationoptical axis 100 ax in FIG. 2B),” as shown in FIG. 2B. The lightincident on the first lenslets in the columns on both sides of thecentral column enters the second lens array 130 along optical axes thatapproach the reference plane. The light incident on the first lensletsin the outermost columns among the plurality of lenslets 122 enters thesecond lens array 130 along optical axes that extend away from thereference plane.

The polarization conversion element 140 changes the polarizationdirections of the sub-light fluxes having been divided by the first lensarray 120 and having passed through the second lens array 130 to analigned polarization direction and outputs light fluxes havingsubstantially one type of linearly polarized light component (polarizedlight fluxes). The polarization conversion element 140 is formed of aplurality of columns of polarization conversion units that convert thelight fluxes from the plurality of second lenslets 132 into polarizedlight fluxes on a column basis, and the number of columns of thepolarization conversion units is four, as shown in FIGS. 1 and 2B.Reference characters 140 a to 140 d in FIG. 2B denote the polarizationconversion units. In the illuminator 100, the number of columns (four)of the polarization conversion units is fewer than the number of columns(five) of the first lenslets 122 and the second lenslets 132, or thenumber of columns of the first lenslets 122 and the second lenslets 132is greater than the number of columns of the polarization conversionunits by one.

The interval P between the thus arranged polarization conversion unitsis greater than the width W of each of the first lenslets 122, as shownin FIG. 2B.

Each of the polarization conversion units 140 a to 140 d includes apolarization separation layer that transmits one of the linearlypolarized light components contained in the light from the light source110 and reflects the other linearly polarized light component in thedirection perpendicular to the illumination optical axis 100 ax, areflection layer that reflects the other linearly polarized lightcomponent having been reflected off the polarization separation layer inthe direction parallel to the illumination optical axis 100 ax, and awave plate that converts the other linearly polarized light componenthaving been reflected off the reflection layer into the one linearlypolarized light component.

The polarization conversion units 140 a, 140 b and the polarizationconversion units 140 c, 140 d are disposed on opposite sides of andsymmetrically with respect to the illumination optical axis 100 ax.

In the illuminator 100, the light incident on the first lenslets 122 inthe central column passes through the second lenslets 132 in the centralcolumn and enters the polarization conversion units 140 b and 140 c. Thelight incident on the first lenslets 122 in the columns on both sides ofthe central column passes through the second lenslets 132 in the columnson both sides of the central column and enters the polarizationconversion unit 140 b or 140 c. The light incident on the first lenslets122 in the outermost columns passes through the second lenslets 132 inthe outermost columns and enters the polarization conversion unit 140 aor 140 d. That is, each of the polarization conversion units 140 a and140 d converts the light from the second lenslets 132 in a single columninto polarized light, and the polarization conversion units 140 b and140 c together convert the light from the second lenslets 132 in threecolumns into polarized light.

The superimposing lens 150 is an optical element that collects thesub-light fluxes from the polarization conversion element 140 andsuperimposes them in the vicinity of the image formation areas of theliquid crystal light modulators 400R, 400G, and 400B. The superimposinglens 150 is so disposed that the optical axis thereof substantiallycoincides with the illumination optical axis 100 ax. The superimposinglens 150 may be a compound lens formed of a combination of a pluralityof lenses.

The color separation/light guiding system 200 includes dichroic mirrors210 and 220, reflection mirrors 230, 240, and 250, and relay lenses 260and 270. The color separation/light guiding system 200 has a function ofseparating the light from the illuminator 100 into red light, greenlight, and blue light and guiding the red light, the green light, andthe blue light to the respective liquid crystal light modulators 400R,400G, and 400B, which are target objects to be illuminated.

Collector lenses 300R, 300G, and 300B are disposed between the colorseparation/light guiding system 200 and the liquid crystal lightmodulators 400R, 400G, 400B.

Each of the dichroic mirrors 210 and 220 has a wavelengthselection/transmission film formed on a substrate, the wavelengthselection/transmission film reflecting light in a predeterminedwavelength range and transmitting light in the other wavelength range.

The dichroic mirror 210 reflects the red light component and transmitsthe green and blue light components.

The dichroic mirror 220 reflects the green light component and transmitsthe blue light component.

The red light reflected off the dichroic mirror 210 is reflected off thereflection mirror 230, passes through the collector lens 300R, and isincident on the image formation area of the liquid crystal lightmodulator 400R for red light.

The green light and the blue light pass through the dichroic mirror 210,and only the green light is reflected off the dichroic mirror 220,passes through the collector lens 300G, and is incident on the imageformation area of the liquid crystal light modulator 400G for greenlight.

The blue light having passed through the dichroic mirror 220 travelsalong the relay lens 260, the light incident-side reflection mirror 240,the relay lens 270, the light exiting-side reflection mirror 250, andthe collector lens 300B and is incident on the image formation area ofthe liquid crystal light modulator 400B for blue light. The relay lenses260 and 270 and the reflection mirrors 240 and 250 have a function ofguiding the blue light component having passed through the dichroicmirror 220 to the liquid crystal light modulator 400B.

The reason why the relay lenses 260 and 270 are provided along theoptical path for blue light is to compensate the optical path length forblue light, which is longer than the optical path lengths for the redlight and the green light, so that the blue light can be usedefficiently without being affected, for example, by divergence of theblue light. In the projector 1000 according to the embodiment, which isconfigured to compensate the longer optical path length for blue light,the optical path for red light may alternatively include a relay lensand a reflection mirror so that the optical path length for red lightincreases.

The liquid crystal light modulators 400R, 400G, and 400B, which modulatethe light from the illuminator 100 in accordance with image information,modulate the color light fluxes incident thereon in accordance withimage information to form a color image. Although not shown, lightincident-side polarizers are interposed between the collector lenses300R, 300G, 300B and the liquid crystal light modulators 400R, 400G,400B, and light exiting-side polarizers are interposed between theliquid crystal light modulators 400R, 400G, 400B and the cross dichroicprism 500. The light incident-side polarizers, the liquid crystal lightmodulators, and the light exiting-side polarizers modulate the colorlight fluxes incident thereon.

Each of the liquid crystal light modulators 400R, 400G, and 400B is atransmissive liquid crystal light modulator that encapsulates and sealsa liquid crystal material, which is an electro-optic substance, betweena pair of transparent glass substrates. For example, a polysilicon TFTis used as a switching device to modulate the polarization direction ofone type of linearly polarized light having exited through each of thelight incident-side polarizers in accordance with a given image signal.The exterior shape of the image formation area of each of the liquidcrystal light modulators 400R, 400G, and 400B is a rectangle having atransverse/longitudinal (x-axis direction/y-axis direction) ratio of4:3).

The cross dichroic prism 500 is an optical element that combines opticalimages carried by the modulated color light fluxes having exited throughthe light exiting-side polarizers to form a color image. The crossdichroic prism 500 is formed by bonding four right-angle prisms and thushas a substantially square shape in a plan view. Dielectric multilayerfilms are formed on the substantially X-shaped interfaces between thebonded right-angle prisms. The dielectric multilayer film formed on oneof the substantially X-shaped interfaces reflects the red light, whereasthe dielectric multilayer film formed on the other interface reflectsthe blue light. These dielectric multilayer films deflect the red lightand the blue light, which then travel in the same direction as the greenlight, whereby the three color light fluxes are combined.

The color image having exited from the cross dichroic prism 500 isprojected through the projection system 600 on a screen SCR.

Advantageous effects provided by the illuminator 100 and the projector1000 according to the embodiment will next be described.

In the illuminator 100 according to the embodiment, since the number ofcolumns of the polarization conversion units is fewer than the number ofcolumns of the first lenslets 122 and the second lenslets 132, theilluminator 100 can use light more efficiently than an illuminator ofrelated art, as shown in Experimental Example described later.

Further, the illuminator 100 according to the embodiment, which includesthe lens integrator system and the polarization conversion element 140as in the case of an illuminator of related art, can output polarizedlight having a homogenized in-plane optical intensity distribution andhence can be suitably used with an apparatus using “polarized lighthaving a homogenized in-plane optical intensity distribution.”

Moreover, the illuminator 100 according to the embodiment, in which theinterval P between the arranged polarization conversion units is greaterthan the width W of each of the first lenslets 122, can use light moreefficiently.

Further, in the illuminator 100 according to the embodiment, since thenumber of columns of the first lenslets 122 and the second lenslets 132is greater than the number of columns of the polarization conversionunits by one, and the number of columns of the first lenslets 122 andthe second lenslets 132 is an odd number, the optical path can bereasonably set with the number of columns of the first lenslets and thesecond lenslets not being greatly different from the number of columnsof the polarization conversion units.

Further, in the illuminator 100 according to the embodiment, since thenumber of columns of the first lenslets 122 and the second lenslets 132is five and the number of columns of the polarization conversion unitsis four, the lens integrator system and the polarization conversionelement can be configured in a relatively similar manner in which thosetypically used at present are configured, whereby the optical path canbe reasonably set.

Further, the illuminator 100 according to the embodiment, in which thelight incident on the first lenslets 122 in the central column among theplurality of first lenslets 122 is incident on the second lens array 130along an optical axis extending along the reference surface, the lightincident on the first lenslets 122 in the columns on both sides of thecentral column is incident on the second lens array 130 along opticalaxes that approach the reference surface, and the light incident on thefirst lenslets 122 in the outermost columns among the plurality of firstlenslets 122 is incident on the second lens array 130 along optical axesthat extend away from the reference surface, allows the light from thesecond lens array to be outputted as polarized light through thepolarization conversion units arranged in a reduced number of columns.

The projector 1000 according to the embodiment, which includes theilluminator 100 according to the embodiment capable of using light moreefficiently than an illuminator of related art, uses light efficiently.

The invention is suitably applicable to the projector 1000 describedabove including liquid crystal light modulators as the light modulators.

EXPERIMENTAL EXAMPLE

FIGS. 3A and 3B describe an illuminator 100 a according to ExperimentalExample. FIG. 3A shows a first lens array 120 a viewed from the sidewhere a second lens array 130 a is present, and FIG. 3B shows how lightis divided in the illuminator 100 a. In FIG. 3B, a superimposing lens150 a is omitted.

FIGS. 4A and 4B describe another illuminator 100 b according toExperimental Example. FIG. 4A shows a first lens array 120 b viewed fromthe side where a second lens array 130 b is present, and FIG. 4B showshow light is divided in the illuminator 100 b. In FIG. 4B, asuperimposing lens 150 b is omitted.

FIG. 5 shows how light is divided in another illuminator 100 c accordingto Experimental Example. In FIG. 5, a superimposing lens 150 c isomitted.

A simulation for evaluating how efficiently an illuminator uses lightwas made on the illuminators according to Experimental Example, theilluminators 100 a and 100 b configured in the same manner as anilluminator of related art and the illuminator 100 c defined inaccordance with the invention.

The illuminators 100 a, 100 b, and 100 c include a common light sourceand a common concave lens but differ from one another in terms of theconfiguration of the first lens array, the second lens array, and thepolarization conversion element. Reference character c2 in FIG. 3Bdenotes the center of the light source in the simulation, so doreference character c3 in FIG. 4B and reference character c4 in FIG. 5.

The simulation was first made on the illuminator 100 a. The first lensarray 120 a in the illuminator 100 a has a plurality of first lenslets122 a (not labeled in FIG. 3A or 3B) arranged in a matrix of eight rowsand six columns, as shown in FIG. 3A. Although not described withreference to FIG. 3A or 3B, the second lens array 130 a also has aplurality of second lenslets 132 a (not labeled in FIG. 3A or 3B)arranged in a matrix of eight rows and six columns. In a polarizationconversion element 142, the number of columns of polarization conversionunits is six, as shown in FIG. 3B. Reference characters 140 e to 140 jin FIG. 3B denote the polarization conversion units.

With reference to the optical intensity (100.0%) obtained in thesimulation made on the illuminator 100 a, results from the followingsimulations were evaluated. That is, the intensity of the light emittedfrom the light source is set to be the same value in all theilluminators, whereby the illuminators can be evaluated in terms of howefficiently they use light by comparing the resultant intensities of thelight outputted from the illuminators.

The simulation was next made on the illuminator 100 b. The first lensarray 120 b in the illuminator 100 b has a plurality of first lenslets122 b (not labeled in FIG. 4A or 4B) arranged in a matrix of six rowsand four columns, as shown in FIG. 4A. Although not described withreference to FIG. 4A or 4B, the second lens array 130 b also has aplurality of second lenslets 132 b (not labeled in FIG. 4A or 4B)arranged in a matrix of six rows and four columns. In a polarizationconversion element 144, the number of columns of polarization conversionunits is four, as shown in FIG. 4B. Reference characters 140 k to 140 nin FIG. 48 denote the polarization conversion units.

The resultant optical intensity obtained in the simulation made on theilluminator 100 b was 100.8%, which indicates that the illuminator ofrelated art can hardly use light more efficiently by reducing the numberof columns of the polarization conversion units.

The simulation was lastly made on the illuminator 100 c. A first lensarray 120, a second lens array 130, and a polarization conversionelement 140 in the illuminator 100 c are configured in the same manneras the first lens array 120, the second lens array 130, and thepolarization conversion element 140 in the illuminator 100 according tothe embodiment, and no redundant description will therefore be made.

The resultant optical intensity obtained in the simulation made on theilluminator 100 c was 106.7%, which indicates that setting the number ofcolumns of the polarization conversion units to be fewer than the numberof columns of the first and second lenslets allows the illuminator touse light more efficiently than an illuminator of related art.

The invention has been described with reference to the above embodiment,but the invention is not limited thereto. The invention canalternatively be implemented in a variety of aspects to the extent thatthey do not depart from the substance of the invention. For example, thefollowing variations can be employed.

1. The dimension, number, material, and shape of each of the componentsdescribed in the above embodiment are presented by way of example andcan be changed to the extent that the change does not compromise theadvantageous effects of the invention.

2. In the embodiment described above, the reflector 20 has anellipsoidal reflection surface, but the reflector 20 is not necessarilyconfigured this way in the invention. For example, the reflector mayalternatively have a parabolic reflection surface. In this case, nooptical element corresponding to the concave lens 90 in the embodimentis required because the reflector can output collimated light.

3. In the embodiment described above, a transmissive projector isemployed, but the invention is not necessarily limited thereto. Forexample, a reflective projector may be employed. The word “transmissive”used herein means that each light modulator as a light modulating deviceis of light-transmitting type, such as a transmissive liquid crystallight modulator, and the word “reflective” used herein means that eachlight modulator as a light modulating device is of light-reflectingtype, such as a reflective liquid crystal light modulator. When theinvention is applied to a reflective projector, the same advantageouseffects as those provided in a transmissive projector can also beprovided.

4. The above embodiment has been described with reference to a projectorusing three liquid crystal light modulators, but the invention is notlimited thereto. The invention is also applicable to a projector usingone liquid crystal light modulator, a projector using two liquid crystallight modulators, and a projector using four or more liquid crystallight modulators.

5. The invention is applicable not only to a front projection projectorthat projects a projection image from the observation side but also to arear projection projector that projects a projection image from the sideopposite the observation side.

6. The above embodiment has been described with reference to the casewhere the illuminator according to the embodiment of the invention isused in a projector, but the invention is not limited thereto. Forexample, the illuminator according to the embodiment of the inventioncan be used in other optical apparatus (such as optical disk apparatus,head lamp of automobile, and illumination apparatus).

The entire disclosure of Japanese Patent Application No. 2011-011688,filed Jan. 24, 2011 is expressly incorporated by reference herein.

1. An illuminator comprising: a light source that emits light; a firstlens array including a plurality of first lenslets; a second lens arrayincluding a plurality of second lenslets corresponding to the pluralityof first lenslets; a polarization conversion element that converts lightfluxes from the second lens array into polarized light fluxes andoutputs the polarized light fluxes; and a superimposing lens thatsuperimposes sub-light fluxes from the polarization conversion element,wherein the plurality of first lenslets and the plurality of secondlenslets are each arranged in a matrix, the polarization conversionelement is formed of a plurality of columns of polarization conversionunits that convert the light fluxes from the plurality of secondlenslets into the polarized light fluxes on a column basis, and thenumber of columns of the polarization conversion units is fewer than thenumber of columns of the first lenslets and the second lenslets.
 2. Theilluminator according to claim 1, wherein the interval between thearranged polarization conversion units is greater than the width of eachof the first lenslets.
 3. The illuminator according to claim 1, whereinthe number of columns of the first lenslets and the second lenslets isgreater than the number of columns of the polarization conversion unitsby one, and the number of columns of the first lenslets and the secondlenslets is an odd number.
 4. The illuminator according to claim 3,wherein the number of columns of the first lenslets and the secondlenslets is five, and the number of columns of the polarizationconversion units is four.
 5. The illuminator according to claim 4,wherein light incident on the first lenslets in a column positionedalong a center line (hereinafter referred to as central column) amongthe plurality of first lenslets enters the second lens array along anoptical axis extending along “a plane that contains a central axis ofthe first lens array and extends along the columns of the first lensarray (hereinafter referred to as reference plane),” light incident onthe first lenslets in columns on both sides of the central column entersthe second lens array along optical axes that approach the referenceplane, and light incident on the first lenslets in outermost columnsamong the plurality of first lenslets enters the second lens array alongoptical axes that extend away from the reference plane.
 6. A projectorcomprising: the illuminator according to claim 1; a light modulator thatmodulates light from the illuminator in accordance with imageinformation; and a projection system that projects light from the lightmodulator.
 7. A projector comprising: the illuminator according to claim2; a light modulator that modulates light from the illuminator inaccordance with image information; and a projection system that projectslight from the light modulator.
 8. A projector comprising: theilluminator according to claim 3; a light modulator that modulates lightfrom the illuminator in accordance with image information; and aprojection system that projects light from the light modulator.
 9. Aprojector comprising: the illuminator according to claim 4; a lightmodulator that modulates light from the illuminator in accordance withimage information; and a projection system that projects light from thelight modulator.
 10. A projector comprising: the illuminator accordingto claim 5; a light modulator that modulates light from the illuminatorin accordance with image information; and a projection system thatprojects light from the light modulator.
 11. The projector according toclaim 6, wherein the light modulator is a liquid crystal lightmodulator.
 12. The projector according to claim 7, wherein the lightmodulator is a liquid crystal light modulator.
 13. The projectoraccording to claim 8, wherein the light modulator is a liquid crystallight modulator.
 14. The projector according to claim 9, wherein thelight modulator is a liquid crystal light modulator.
 15. The projectoraccording to claim 10, wherein the light modulator is a liquid crystallight modulator.